I've been an author and book publisher for quite a while now, and I've had quite a lot of success with social media marketing, blogging, and PPC advertising to sell my books. But I'm new to the world of email marketing. I'm hoping there are people here who can give me advice on how to grow my subscriber list.
So far, I've been buying solo ads and that has helped to a degree. I've also posted links to my opt-in pages on my blog, my company's website, and regularly on Twitter. I was advised to also use forums to drive more traffic, but I've been unsuccessful with this on the writer/author forums I've subscribed to.
What advice do you have for me on the best ways to grow one's subscriber list?
Thanks in advance for your help.